Drugs that widen the airways to ease breathing difficulties
Bronchodilator drugs are used to dilate (widen) the bronchi (airways) inside the lungs (see How bronchodilator drugs work). Widening the airways prevents or relieves the wheezing, tightness of the chest, and shortness of breath that can result from conditions such as asthma and chronic obstructive pulmonary disease, a progressive disease of the lungs.
Many bronchodilator drugs are inhaled through a metered-dose inhaler, a small aerosol pump that delivers a controlled amount of the drug to be inhaled into the lungs. Spacers, which are plastic chambers into which a dose of the drug is released before it is inhaled, and breath-activated inhalers are also available. You may prefer to use a spacer if you have difficulty using an inhaler on its own (see Taking inhaled asthma drugs). If you have severe shortness of breath, you may need to take bronchodilator drugs by means of a nebulizer, a device that delivers the drug in aerosol form through a mask or a mouthpiece. Certain bronchodilators are taken orally on a regular basis to prevent asthma attacks occurring.
During any discussion about your bronchodilator treatment, you should let your doctor know if you are pregnant or breast-feeding.
What are the types?
Bronchodilator drugs are divided into three main groups: sympathomimetics, anticholinergics, and xanthines. When inhaled, some sympathomimetics take effect within 10 minutes and are often used for rapid relief from shortness of breath; anticholinergics and xanthines are slower acting. Two or more types of drug may be used simultaneously.
These are the most commonly used bronchodilators. They relax muscles in the wall of the airways, causing the airways to widen.
These drugs are usually inhaled and are of two main types: short-acting and longer-acting. Short-acting types, such as salbutamol, act within minutes and remain effective for 4–6 hours. Other types, such as salmeterol, are slower acting and longer lasting, taking up to 4 hours to act and lasting for about 12 hours. Formoterol acts rapidly and also lasts for about 12 hours.
Usually, inhaled sympathomimetics are used at the first sign of symptoms or to prevent symptoms developing, for instance before physical activity. These drugs may cause slight tremor, agitation, insomnia, and, rarely, a rapid heartbeat.
The drugs in this group are often used in combination with sympathomimetics to treat chronic obstructive pulmonary disease. Anticholinergics work in a similar way to sympathomimetics. They may cause some side effects, including a dry mouth, difficulty in passing urine, and blurred vision. In rare cases, they may trigger an attack of acute glaucoma, an eye disorder that can permanently damage vision and needs immediate treatment.
These bronchodilator drugs have a prolonged action, which makes them useful in preventing night-time asthma attacks. Xanthines act on the muscle cells of the airway walls, causing the airways to widen.
Oral xanthines may be taken daily as a preventive measure. If you have a severe attack of shortness of breath, you may be given aminophylline intravenously through a drip. These drugs sometimes cause nausea and headache and, taken in high doses, occasionally produce a rapid and irregular heartbeat. For this reason, xanthines are used less commonly than other bronchodilators.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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